A drug commonly used to treat diabetes could help those living with Parkinson’s disease, research has revealed.

By 2020 it is predicted that 162,000 individuals in the UK will be living with the condition. While existing drugs help to control its symptoms, there are currently none available which slow or halt its progression.

But now scientists say they have found that a drug commonly used to treat type 2 diabetes appears to improve movement-related issues.

The benefit persisted even when the drug had not been taken for 12 weeks, suggesting it might be helping to slow the progression of the disease.

“It is not ready for us to say ‘well, everyone needs to start this drug’,” said Thomas Foltynie, professor of neurology at University College London and co-author of the study. “[But] if we can replicate these findings in a multicentre trial, especially with longer follow-up, then this can change the face of our approach to treating Parkinson’s.”

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Writing in the Lancet, Foltynie and colleagues in the UK and US describe how they tested the impact of the drug, known as exenatide.

But the latest study is the first robust clinical trial of the drug, randomly allocating 60 people with Parkinson’s to one of two treatments – either receiving injections of exenatide or a placebo once a week.

At the start of the study and then every 12 weeks, participants in both groups were assessed on a disease-severity scale based on movement – including tremors, stiffness of the limbs and ability to recover balance. The assessment was carried out at the start of the day, before participants had taken their usual medication, and again once the medication had been taken.

With no medication, people with Parkinson’s are expected to drop about three points on the 132-point assessment scale every year, but after 48 weeks the morning tests of those taking exenatide showed a one-point improvement while those taking the placebo showed a three-point drop.

When the patients were assessed 12 weeks later, the team found that those who had been treated with exenatide were 3.5 points higher on the scale compared to those taking the placebo, even after controlling for various factors including disease severity.

The authors say the study suggests exenatide might not just help control symptoms of Parkinson’s, but could be helping to slow the progression of the disease, although they admit further research is needed.

“What we have shown is that there is a 3.5 point advantage in using this drug. Now if that is all you get, then that is quite trivial,” said Foltynie. “But if it is a cumulative advantage – so if after two years patients on placebo were six points worse and the exenatide group were stable … then we have actually stopped disease progression and that is of enormous value.”

Others were also cautiously optimistic.

“I think it is a really exciting step forward,” said Dr Heather Mortiboys, an expert in neurodegenerative diseases at the University of Sheffield, pointing out that the use of repurposed drugs could expedite treatment compared with developing treatments from scratch. But, she noted, no clear effects were seen in brain scans of the participants and it was unclear how exactly how the drug was working.

David Dexter, deputy director of research at Parkinson’s UK, said the study was encouraging. .

“The small benefits seen in this study are particularly promising because only a low level of the drug injected actually reached the brain,” he said. “This suggests that finding treatments that work in a similar way, but are better able to cross from the bloodstream into the brain, may be even more effective.’